A LEVELLING SYSTEM FOR WORK MACHINES

The present invention relates to a levelling system for self-propelling work machines predisposed for lifting loads, especially cranes for trucks, or the like.

Cranes are known, comprising a respective articulated and / or extensible arm predisposed on a motor truck and mainly used for loading and unloading material from and onto a truck body on the truck.

With the aim of safely moving the load, the crane must be stabilised using appropriate devices, called "outriggers", predisposed on the support frame of the truck body and /or on the crane.

The outriggers are usually of the telescopic type, hydraulically activated, and have the aim of preventing a tipping of the machine during the operating steps.

In detail, two cross-members can be provided, arranged perpendicular to the axis of the motor truck and reciprocally joined by a pair of longitudinal members, two shafts being slidably inserted in each of the cross- members, which shafts bear, at distal ends thereof, respective rest feet, mounted on vertically-mobile outrigger jacks.

In practice, during the driving condition, the outriggers are in a retracted configuration, in which they have a minimum lateral dimension with respect to the advancement direction of the truck.

Before the loading and unloading steps, the outriggers must be brought into an extended configuration, in which the respective shafts are extracted from the relative cross-member so as to project at the flanks of the vehicle, and the feet are lowered down to the ground.

Often the machines must be stabilised on a surface, which can have irregularities or be uneven.

In these circumstances, the operator has to make judgement on the levelness of the machines on which the load lift system is mounted, with regards to the horizontal plane ensuring that the vehicle is "levelled" correctly, as a substantial inclination thereof might increase the risk of tipping over during the manoeuvring of the load lifting device.

At present, the procedure followed for compensating the uneven level of the frame is the following.

The operator has available a mechanical level mounted on-board the vehicle which indicates the inclination of the vehicle and a radio command with which she or he can regulate the activating of the outriggers, in particular the vertical excursion of the jacks which bear the rest feet.

By walking around the means and performing visual assessments, the operator proceeds by trial and error to modify the thrust of the various outrigger jacks in an attempt to bring the frame into a position as horizontal as possible, and cyclically checking the level to see if the result has been attained.

The known system has some drawbacks, described in the following.

Firstly, the effectiveness of the known levelling procedure is largely dependent on the individual abilities of the single operator.

Therefore, an inexpert or barely able operator might not correctly level the vehicle, with a consequent risk of loss of stability of the vehicle during the steps of movement of the load by the crane.

Further, the mechanical levels used in the known systems notoriously have rather high measuring tolerances, even up to three degrees, which results in uncertainty for the operator with regard to whether the vehicle is correctly levelled or not.

The technical task underpinning the present invention is therefore to provide an improved automatic levelling method and system which obviates the drawbacks of the prior art.

The technical task is attained by the levelling system realised in accordance with claim 1 and by the method actuated according to claim 1 1 .

Further characteristics and advantages of the present invention will become more apparent from the following indicative, and hence non- limiting, description of preferred, but not exclusive, embodiments of the system of the invention, as illustrated in the accompanying drawings, in which:

figures 1 and 2 are axonometric views of a vehicle on which the system of the invention has been mounted, in various operating steps of stabilisation;

figures 3 and 4 are schematic front views of the vehicle of the preceding figures, which show various steps of the levelling operation actuated by the system of the invention;

- figures 5 and 6 are front views of an outrigger of the invention, in two different operating instants of the operation thereof; and

figure 7 is a diagram illustrating the processing unit of the invention. With reference to the accompanying figures, reference numeral 1 denotes in its entirety a work machine with which the system of the invention can be used.

In detail, the levelling system of the invention is especially destined for use with a self-propelling work machine 1 for lifting loads, preferably cranes for trucks.

The invention is preferably used with a hydraulic crane 10, provided with an articulated and/or extensible arm predisposed telescopically on the frame 100 (or "chassis") of the truck 1 and able to be used for loading and unloading material onto and from the truck body of the truck 1 , located on the frame.

For reasons of clarity of understanding of the figures, in the appended tables of drawings the truck body has not been illustrated.

The arm of the crane 10 is preferably mounted on a rotating turret located immediately behind the cabin 1 1 and, in turn, at a distal end thereof has a lift hook mounted.

The system of the invention includes a plurality of outriggers 2 mobile between a retracted rest configuration and at least an extended use configuration. Further, the system comprises an activating apparatus 3, preferably of an electro-hydraulic type, such as for example a proportional hydraulic distributor 3 mounted on the crane or on the frame 100 of the vehicle 1 and able to selectively activate the outriggers 2 and regulate functioning thereof.

In practice, each outrigger 2 can be gradually, in a regulated way, and singly, activated, by means of hydraulic actuators comprised therein.

In the invention, the distributor 3 (or other apparatus) is able to receive command signals and can cause passage of the outriggers 2 from one configuration to another as a function of the command signals received. In general, the system of the invention can include a plurality of hydraulic actuators, for example hydraulic cylinders, predisposed for moving the outriggers 2 and for moving the arm of the crane 10, subjected to at least a hydraulic distributor 3, in turn subjected to a processing unit 4, of which more in the following.

In the illustrated preferred embodiment, the system includes the use of four outriggers 2 predisposed on the support frame 100 of the truck body, subdivided into a front pair and a rear pair, thus providing two outriggers 2 for each flank of the machine 1 .

A case is possible in which only two outriggers 2 are present, for example arranged immediately behind the cabin.

Returning to the preferred embodiment of the invention, two cross- members 20 can be included, arranged perpendicular to the axis of the truck 1 and reciprocally joined by a pair of longitudinal members 200, defining a counterframe fixed above the chassis of the truck 1 .

Two telescopic shafts 21 are slidably inserted in each of the cross- members 20, which bear, at the distal ends thereof, respective rest feet 22, which are vertically mobile.

More precisely, the shafts 21 are preferably located horizontally and the rest feet 22 are borne by outrigger jacks 23 or other extensible thrust elements, preferably arranged vertically; in detail, each jack 23 can be telescopic, preferably has one segment and is located at the distal end of the respective shaft 21 .

In still greater detail, the shafts 21 are substantially perpendicular to the longitudinal axis of the machine 1 and can be substantially mutually coplanar; in practice, they are positioned in a parallel plane to the plane in which the frame 100 of the machine 1 extends.

The outrigger jacks 23 are preferably substantially perpendicular to the relative shafts 21 .

Therefore, if the machine 1 is rested on a flat ground surface S, the shafts 21 of the outriggers are parallel to the ground surface and the jacks 23 are perpendicular thereto; if the ground surface is horizontal, then the jacks 23 are vertical.

The extraction of the shafts 21 and the descent of the feet 22 are obviously operated by the above-mentioned actuators when the distributor 3 is activated.

As is visible in the appended figures, which illustrate a preferable but not limiting embodiment of the invention, a cross-member 20 is located immediately behind the cabin 1 1 , while the other cross-member 20 is arranged behind the rear axle.

During the movement of the vehicle 1 , the outriggers 2 are in a retracted rest configuration, in which they have a minimum lateral dimension with respect to the advancement direction of the truck 1 , while, in use, the outriggers 2 are in one of the extended working configurations.

Further, the invention can include a radio command device 6 (or other portable command device) able to produce and transmit pilot signals as a function of the selections made by the operator 5.

In general terms, the interface of the portable command device 6 is configured for enabling a setting of at least a command parameter representing a variation of the configuration of at least an outrigger 2 of the system.

The proportional distributor 3 is able to singly command the outriggers, by separately regulating the extension of the shafts 21 and the descent of the feet 22, together also with the pressure exerted by the jack 23 when the feet 22 touch the ground surface; therefore, preferably, the radio command 6 is configured for independently piloting each outrigger 2, going to regulate the excursion of the shaft 21 and the excursion of the rod of the jack 23.

In a case where the command device is a radio command 6, the interface can comprise at least a command lever and, for example, one or more buttons; it does not exclude the possibility that the interface is constituted by a touchscreen display alternatively or in addition to levers and buttons and / or the interface enables vocal commands or includes other means for setting said command parameters.

In the following, for reasons of clarity of illustration and without departing from the general description, reference will be made by way of non-limiting example to a case in which the command device is a radio command 6 equipped with command levers for the operation of the outriggers 2.

In an important aspect of the invention, the system includes at least an electronic measuring device of the inclination 7, for example a digital level (represented only schematically in figure 7), mounted on the frame 100 of the machine 1 or in any case associated to the frame 100.

In practice, the level 7 (or other like device) can be mounted directly on the frame 100 or on a rotationally solid element, such as the above-mentioned cross-members 20 or even the shafts 21 or the crane.

The function of the level 7 is to establish the degree of inclination of the frame 100, and therefore instant by instant, in particular with respect to the horizon or the vertical; in the following, reference will be made by way of example to a case where the level 7 measures the inclination of the frame 100 with respect to the horizon, a datum which can in any case be certainly extracted from the measuring of the inclination with respect to directions that are rigidly solid with the axis of the frame 100 or other fixed references with respect thereto. More in general, the measuring device 7 is able to detect the inclination degree of a reference element of the machine 1 , which is preferably the support frame 100 but can also be the base of the crane or another element solidly constrained to the frame 100 itself.

For reasons of illustrative simplicity, in figure 4 this inclination is indicated by angle A, formed between the ground surface S and a lower edge of the frame 100, which is presumed to be straight.

The level 7 can be positioned centrally of the frame 100, both in the length direction and in the width direction, with the aim of determining a characteristic inclination value or there can be a plurality of levels distributed on the frame 100, in order to calculate an average value or for also determining torque values; these verifications and calculations are carried out by the processing unit 4 connected to the inclination measuring device, whether this is a digital level 7 or not.

More precisely, the inclination-measuring device 7 is able to produce inclination signals that are a function of the inclination measured, which are directed to the processing unit 4 via cabling or radio signals or other transmission means.

The processing unit 4 is therefore able to receive and process the inclination signals and comprises a levelling module 41 configured for producing said command signals for the distributor 3 (or other activating apparatus).

The command signals produced by the processing unit 4 are able to modify the extension of the rods of the above-said jacks 23 included in the outriggers 2 as a function of the inclination A measured.

However, the processing unit 4 can be constituted by a single electronic device, including of the type commonly present on this type of machine, suitably programmed for carrying out the functions described.

Alternatively, the processing unit 4 can be "distributed" and therefore constituted by a plurality of electronic devices.

In general, the processing unit 4 can make use of one or more microprocessors or microcontrollers for carrying out the instructions contained in memory modules and in the functional modules thereof; the microprocessors or microcontrollers can further be distributed over a plurality of local or remote calculators that can also constitute a network. The invention thus enables automatically levelling the work machine 1 by means of the outriggers 2, due to the fact that the inclination A can be assessed in real time, with significant precision, and enables compensating the uneven levels or irregularities of the ground surface S on which the machine 1 is to be operated.

Before illustrating further preferable specifications of the invention, there follows a brief description of the basic functioning thereof.

The machine 1 is brought to the site where the crane is to be used for carrying out the lifting and displacing operations of loads.

The operator commands the opening and the resting of the outriggers 2, for example by means of the above-mentioned radio command 6.

Once the stabilising step has been completed, the automatic levelling step is performed.

If the ground surface S on which the machine 1 is not horizontal (as in the case of figure 4), the digital level 7 detects the inclination A and, on the basis of this, the processing unit 4 produces command signals which lead the distributor 3 to selectively activate the outriggers 2 so as to compensate for the unevenness.

More precisely, the outrigger jacks 23 which are on the lower side of the machine 1 are activated to thrust and thus raise the machine 1 up to when the frame 100 is horizontal or in any case in an acceptable condition of inclination.

In other words, the outrigger jack 23 which is in the lower position is hydraulically activated so that the thrust rod thereof slides perpendicularly to the ground surface S, the adjustment of the pressure with which the jack 23 is piloted, and therefore the sliding excursion of the rod, being regulated by the proportional distributor 3 as a function of the commands received from the processing unit 4.

The levelling module 41 is preferably configured for producing said command signals for modifying the activating of the jacks 23, as long as an absolute value of the inclination A measured is greater than a levelling threshold.

In other words, via a memory module 42, a range of angles of inclination considered acceptable can be preset in the processing unit 4, for example between +0.5 and - 0.5 degrees and the processing unit 4 will continue to command a thrusting action on the jacks 23 located lower, up to when the value of the inclination A measured by the digital level 7 enters the acceptable range.

It is possible that, with the aim of obtaining the ideal levelling, it might be necessary, together with a thrust of the jacks 23 positioned lower, for the reduction of the thrust of the jacks 23 positioned higher, with a consequent retraction of the rod bearing the feet 22 rested on the ground surface S. The processing unit 4 can also include an enabling module 43 configured for activating or disabling the levelling module 41 .

To be precise, the radio command 6 or other portable command apparatus can be provided with an interface selectable by an operator 5 for enabling the activating of the automatic levelling step, following the initial stabilisation.

For example, the radio command 6 can comprise an appropriate button which enables activating the enabling module 43 which, on the evidence of measurements of the level 7, selectively commands the outriggers 2. Further, the invention can comprise one or more rest sensors 8

(schematically represented in figure 7), mounted on the work machine 1 and able to verify whether one or more of the wheels 101 thereof are resting on the ground surface S or are raised, and to produce "grounded" signals as a function of the verifications carried out.

In this case, the processing unit 4 is able to receive said grounded signals and the above-mentioned enabling module 43 is configured for activating or disabling the levelling module 41 on a basis of whether said wheels 101 are resting or are raised.

In fact, for some types of work machines 1 , such as for example cranes for trucks, the reference standard provides that all or some wheels 101 (typically the braking wheels) are never separated from the ground surface S during the working steps of the crane.

Therefore, the enabling module 43 can be configured for preventing the outrigger jacks 23, during the levelling step, from lifting the machine 1 to the point of separating the wheels 101 from the ground surface S (either all the wheels or those that must always be grounded).

In practice, following the stabilising step, the processing unit 4 proceeds, if necessary, to command the proportional distributor 3 so that it can pilot the jacks 23 for the compensation of the non-horizontal position of the frame 100, an operation which is concluded either when the frame 100 reaches an acceptable level of inclination A (and preferably nil) or before at least one of the wheels 101 designated always to remain resting on the ground surface is raised.

The above-mentioned rest sensors 8 can be dynamic sensors, for example force sensors associated to the wheels 101 and applied for example to the suspension springs or can be sensors measuring the distance, for example using optic or acoustic technology or can be pressure sensors associated to the tyres or others besides.

As mentioned in the foregoing, in the embodiment in which a plurality of levels 7 (or like devices) is applied to the frame 100, for example two levels 7 at different points of the length of the frame 100, the processing unit 4 can comprise a torque module 44 configured for calculating the torque of the frame 100 about the longitudinal axis thereof.

In this case, the enabling module 43 can be enslaved to the torque module 44 with the purpose of preventing the levelling operations from leading to an excessive torque of the frame 100, which over time might weaken the mechanical resistance thereof. Further, an anti-torque module 45 can be included, configured for commanding the levelling module 41 so that it selectively activates the outriggers 2, and in detail the jacks 23, with the aim of compensating for any strong torque that the frame 100 might have following the initial stabilising step.

In a known way, though not in combination with the other characteristics of the invention, a play can deliberately be left between the shafts 21 of the outriggers 2 and the above-mentioned cross-members, wherein the shafts 21 are inserted, or between two segments comprised in the shaft 21 itself, which play enables the inclination of the shaft 21 in a vertical plane.

In schematic figures 5 and 6, this play is represented between two segments that are a part of the shafts 21 , but this is a non-limiting example chosen because it enables a simpler and clearer graphic representation. Owing to the weight, when a shaft 21 is extracted from the cross-member 20, and before the jack 23 is activated for the purpose of the descent of the foot 22, the shaft 21 has a downwards inclination (figure 5).

Once the stem of the jack 23 has been extended up to pressing, with the foot thereof, on the ground surface S, the play is taken up in an upwards direction (figure 6).

With the application of a sensor 9, the above-described play can be exploited for verifying whether the outrigger 2 has been rested on the ground surface S.

In fact, the rest sensor 9 can be able to verify when the shaft 21 is hanging downwards and when it "loses" the reading when the play is reabsorbed upwards; consider for example a case of a switch applied inferiorly on the outrigger 2 which is pressed by the beam when the beam is freely subjected to the force of gravity.

In this case, when there is an interruption of the signal transmitted by the sensor to the processing unit 4, the processing unit 4 is informed of the fact that the relative outrigger 2 has gone to rest on the ground surface.

In detail, the enabling module 43 can be configured for activating the stabilising module only if all the rest sensors 8 have interrupted transmission of the signal or send, to the processing unit 4, a signal indicating the fact that the play of the beam has been reabsorbed.

Differently, the rest sensor 9 can include detecting when the play of the beam is reabsorbed upwards, transmitting a signal that the resting operation has taken place to the processing unit 4.

In both cases, the enabling module 43 is configured for activating/disabling the stabilising module on the basis of signals received from the rest sensors 8.

The invention also relates to a method for levelling a work machine 1 able to lift loads and comprising a plurality of outriggers 2 mobile between a rest position and at least a working position in which the outriggers can rest on the ground surface S; each outrigger 2 includes an extensible thrust element 23 able to abut on the ground S.

In practice, the method is destined to perform a levelling of a work machine 1 of the above-described type.

The method includes following steps:

- bringing the outriggers 2 to rest on the ground surface S, thus stabilising the machine 1 ;

- determining the inclination A of the frame 100 of the machine 1 relative to the horizon; and

- if the absolute value of the inclination A of the frame 100 is greater than a levelling threshold, modifying the extension of the rod of the jack 23 (or other thrust elements) of one or more outriggers 2 , so as to bring the inclination A of the frame 100 below said threshold.

The method of the invention can comprise further steps corresponding to the functionality of the components of the system of the invention, including the modules of the processing unit 4.

In particular, the method can include verifying whether one or more wheels 101 are rested on the ground surface S or are raised from the ground surface and modifying or maintaining unaltered the extension of the thrust elements 23 according to said verification of the resting of the wheels 101 . It is also possible for the modification of the extension of the thrust elements 23 to be discontinued before at least one of the wheels 101 is raised from the ground surface S.